When sonographically detected movements were correlated with maternal perception, approximately 50 percent of isolated limb movements were perceived by the mother, whereas 80 percent of movements involving both the trunk and limb were perceived in one study [ 1 ]. (uptodate.com)

During the steady-state phase of the pursuit eye movement, target and context moved continuously at 11.3 deg/s, or were independently perturbed for 250 ms to move slower (5.6, 8.5 deg/s) or faster (14.1, 16.9 deg/s). (arvojournals.org)